While conveyors with which the chain of the present invention are intended to be used may have many applications, for purposes of an exemplary showing, such conveyors will be described with respect to their use in the mining industry, although their use is not intended to be so limited.
Pusher-type chain conveyors, as used in the mining industry, are found both in the form of separate conveying units, and as integral parts of continuous mining machines. A typical continuous mining machine, for example, is self-propelled and is provided at its forward end with cutting means shiftable in such a way that an entry is cut in the material being mined. The entry is so sized as to permit the passage of the mining machine therethrough. Since the cutting operation is a continuous one, it is necessary to provide means to move the cut material from in front of the mining machine and to convey it out of the entry. To this end, the mining machine usually incorporates one or several conveyors in its construction, the conveyors acting successively to transport the cut material rearwardly of the machine. Frequently, the mining machine further incorporates a “tail conveyor” which is a part of the mining machine, located at its rearward end. The purpose of the tail conveyor is to deliver the cut material to other conveying means by which it is removed from the entry. The other conveying means may comprise mine cars, portable belt conveyors, or the like.
The most frequently encountered form of tail conveyor, in association with a continuous mining machine, comprises a section of conveyor base means mounted on the mining machine body. One or more additional sections of conveyor base means are connected thereto end-to-end, and extend beyond the rearward end of the mining machine body. All of the base means sections are characterized by a bottom portion provided with longitudinally extending, upstanding side guides or flanges. In order for the tail conveyor to perform its task properly, the various sections thereof must be capable of both lateral and vertical movement with respect to each other. This enables the cut material to be delivered to a desired point despite changes of position of the mining machine as it advances in the entry and changes in level of the entry floor. Similarly, this lateral and vertical movement capability of the conveyor sections enables the shifting of the desired delivery point for the material being mined, as required.
The tail conveyor typically incorporates a continuous pusher-type conveyor chain which is driven along the length of the conveyor base sections. The chain is normally provided with a plurality of rigid pusher elements, normally extending substantially transversely of the conveying direction. The pusher elements are located at spaced intervals along the chain. Adjacent pusher elements are joined together by a series of alternate block-like links and plate-like links. At one end of the machine's conveyor, the continuous chain passes over a driven sprocket. At the other end of the conveyor, the chain passes over a driven or idler sprocket, or roller.
Typically in the underground mining industry, machine downtime is very expensive. Should a conveyor chain fail (due to sudden impact or wear), the chain often would come apart during production causing several hours of expensive and unproductive downtime while the chain was repaired. Most often a conveyor chain fails from impact loads on the flight arms. These impacts over time cause a fracture which then causes the welded-in pins to fail.